Effect of Cartridge Storage Time and Ambient Laboratory Conditions on the Stability of Mechanical Properties of Bis-Acryl Interim Resin Materials.

Abstract

To investigate the stability of mechanical properties during the entire shelf life of chemically-activated bis-acryl interim resin materials stored at ambient laboratory conditions. Four bis-acryl interim resin materials with no explicit recommendation for refrigerator storage were selected (Luxatemp Plus, Visalys Temp, Structur3, Structur Premium). Following cartridge storage at ambient laboratory conditions in 6-month intervals, 30 specimens (2.0 × 2.0 × 25.0mm3 ) were prepared in each case and stored in distilled water (37.0 ± 1.0 °C) with 3 different water storage times (2hours, 24hours, 7days). Flexural strength, modulus of elasticity, modulus of toughness, and elastic recovery were determined (3-point bend test). Data were subjected to a three-way multivariate analysis of variance (MANOVA) to determine overall significance, followed by a series of separate one-way ANOVAs after data were split, using Tukey and Games-Howell posthoc tests to identify significant differences between groups (α = 0.05). While Luxatemp Plus showed no significant decrease for all mechanical properties during the investigated shelf life of 21 months (p > 0.05), Visalys Temp exhibited a continuous decline of the corresponding values (p < 0.05), irrespective of the water storage time. Structur3 and Structur Premium properties remained almost unchanged during the first 6 months of the examination period. Subsequently, a progressive decrease was observed for flexural strength and modulus of elasticity, while most modulus of toughness and elastic recovery results revealed little alteration. Depending on the bis-acryl interim resin material, mechanical properties appeared to be susceptible to continuous degradation processes during cartridge storage at ambient conditions, especially towards the end of the material shelf life. For some materials, the chemical stabilization and recommended storage conditions should be revised by the manufacturers to prevent premature aging during shelf life.